The objectives of this application, submitted to the NIDR Small Grants Program, is to develop a means of isolating putative pre- osteoclasts. Three necessary elements come together in this proposal which make this pilot project likely to succeed: One, a source of large numbers of pre-osteoclasts has been identified; two, a non-toxic fluorescent marker to identify the cells is available; and three, access to a flow cytometer which will allow the sorting of the labeled cells from others is available. Once obtained, the cells will be typed by morphological methods, and their viability, culturability and capacity to fuse to form multinucleate osteoclasts will be assessed. The value of this endeavor is two-fold: First, a reliable source of osteoclasts for in vitro studies will be an invaluable research tool. Two, a system for investigating the mechanism of fusion of precursor cells into osteoclasts will be provided. Understanding osteoclast function has clinical relevance since excessive osteoclast activity is an important aspect of periodontal disease and other diseases where bone loss occurs.